[Breaking] Allow aborting exec, remove execTask

[niik]

As of Node 20 execFile supports an AbortSignal as a means to cancel (i.e. kill) the process. Once the AbortSignal fires Node will take care of sending the specified killSignal (defaults to SIGTERM) to the process unless the process has already run to completion in which case the abort is a noop.

This lets us do away with our custom execTask implementation in favor of relying on Node to do the heavy lifting. In order for callers to be able to detect an abort all errors thrown from Dugite's exec will now be of type ExecError and callers will be able to use the code property to determine the cause of the error.

Example:

GitProcess.exec(
  ['clone', '--progress', 'https://github.com/desktop/dugite'],
  '/tmp/git',
  {
    signal: AbortSignal.timeout(10 * 1000),
  }
)
  .then(() => console.log('Clone completed!'))
  .catch(e =>
    e instanceof ExecError && e.code === 'ABORT_ERR'
      ? console.error('The clone timed out')
      : console.error(e)
  )

This also removes the custom error codes RepositoryDoesNotExistErrorCode and GitNotFoundErrorCode. These were an attempt to provide friendly error codes for implementors but assumed that the callers cared about the distinction between the Git executable missing and the cwd missing. Instead of synchronously stat'ing the path on ENOENT when it's possible that the caller doesn't care we'll leave it up to callers to choose whether to try to detect why the exec failed.

Note that the pathExist approach was subject to race conditions and that there's no guarantee you'd ever be able to figure out exactly why the call failed. Here's an example of mimicking RepositoryDoesNotExistErrorCode and GitNotFoundErrorCode:

const { access } = require('fs/promises')

const pathExist = path =>
  access(path).then(() => true).catch(() => false)

GitProcess.exec(['--version'], '/tmp/donutexist').catch(e =>
  e instanceof ExecError && e.code === 'ENOENT'
    ? pathExist('/tmp/donutexist').then(exists =>
        Promise.reject(new Error(exists ? 'Git not found' : 'Path not found'))
      )
    : reject(e)
)

This also removes the custom message when hitting maxBuffer limits. This message is already decent enough straight from Node.

[sergiou87]

Nice!! This is so much more idiomatic 🥹 👏